How to Choose the Right ETF

🔵 Five Criteria That Actually Matter

You know what ETFs are and why they are useful. But with thousands available, how do you choose the right ETF for your portfolio? This article gives you a practical framework for evaluating and selecting ETFs — based on five factors that actually matter.

The Five Factors That Matter

When comparing ETFs, focus on these five criteria. Everything else is secondary.

1. What Does It Track?

Every ETF follows an index — and that index defines what you are investing in. The most important decision is not which ETF provider to use, but which part of the market you want to own.

Broad market (most diversified):

MSCI World — ~1,500 companies, 23 developed countries
FTSE All-World — ~4,000 companies, developed + emerging markets
MSCI ACWI — ~2,900 companies, similar to FTSE All-World

Regional:

S&P 500 — 500 largest US companies
MSCI Emerging Markets — ~1,400 companies from China, India, Brazil, etc.
SET50 / SET100 — 50 or 100 largest Thai-listed companies

Sector or theme:

Technology, healthcare, clean energy, real estate — focused on one industry
Higher concentration risk, higher potential reward

For most beginners: A single broad-market ETF (MSCI World or FTSE All-World) is the strongest starting point. It gives you global diversification in one purchase. You can add regional or sector ETFs later if you want more specific exposure.

2. How Much Does It Cost?

The expense ratio (TER) is the annual fee you pay for holding the ETF. It is deducted automatically from the fund’s value — you never see a bill, but it reduces your return every year.

Broad market ETFs:     typically 0.05% – 0.25%
Regional ETFs:         typically 0.10% – 0.50%
Sector / theme ETFs:   typically 0.30% – 0.75%
Actively managed ETFs: typically 0.50% – 1.50%

The impact over time:

On ฿1,000,000 invested over 20 years at 7% gross return:

0.10% TER → final value ≈ ฿3,620,000
0.50% TER → final value ≈ ฿3,390,000
1.00% TER → final value ≈ ฿3,070,000

The difference between 0.10% and 1.00% is ฿550,000 — from the same starting amount, the same time period, and the same gross return. The only difference is cost.

Rule of thumb: For broad market exposure, do not pay more than 0.30% TER. There is almost always a cheaper option that tracks the same index.

3. How Big Is the Fund?

Fund size (Assets Under Management / AUM) matters for two practical reasons:

Liquidity: Larger funds are easier to buy and sell without affecting the price. Very small funds (under $50 million) can have wider bid-ask spreads, which increases your trading cost.

Survival: Very small funds risk being closed by the provider if they are not profitable to operate. If a fund closes, you get your money back — but it forces an unplanned sale, potentially at a bad time.

Guideline: Prefer ETFs with at least $100 million in AUM. Above $500 million is ideal. This is rarely a problem with major broad-market ETFs, but becomes relevant for niche or thematic funds.

4. Where Is the Fund Based?

ETFs can be domiciled (legally registered) in different countries. For investors accessing ETFs through a Thai broker, the domicile affects taxes and accessibility.

Ireland-domiciled ETFs (UCITS):

Most common for non-US investors
Lower US dividend withholding tax (15% instead of 30%) due to the Ireland-US tax treaty
Available through most international brokers and via DR/DRx on Thai platforms
ISIN starts with “IE”

US-domiciled ETFs:

Directly listed on US exchanges (NYSE, NASDAQ)
Subject to 30% US dividend withholding tax for non-US investors
Often the cheapest (e.g., Vanguard VTI at 0.03%)
Available through Thai brokers offering US stock access

Thai-domiciled funds:

Regulated by Thai SEC
Bought in Baht, no currency conversion needed
Often higher fees than international equivalents
Tax advantages may apply (RMF, SSF, Thai ESG structures)

For most investors using a Thai broker: Ireland-domiciled UCITS ETFs offer the best combination of tax efficiency, accessibility, and cost. US-domiciled ETFs are cheaper but tax-disadvantaged for non-US investors.

5. Accumulating or Distributing?

ETFs handle dividends in one of two ways:

Accumulating (Acc): Dividends are automatically reinvested into the fund. Your units grow in value over time. No cash payout, no action needed from you. Better for long-term growth and potentially more tax-efficient.

Distributing (Dist): Dividends are paid out to your brokerage account as cash — monthly, quarterly, or annually. You decide what to do with the cash. Provides regular income but requires you to reinvest manually if you want to compound.

For long-term wealth building: Accumulating is generally more efficient — automatic reinvestment means compound interest works without your intervention. Choose distributing only if you specifically need regular income from your investments.

Putting It Together — A Practical Example

Imagine you want a simple, globally diversified stock portfolio. Here is how you might apply the five criteria:

Index:          FTSE All-World (broad, global, ~4,000 companies)
TER:            under 0.25%
Fund size:      over $1 billion
Domicile:       Ireland (UCITS)
Type:           Accumulating

Result:         One ETF. Globally diversified. Low cost.
                Automatic reinvestment. Tax-efficient structure.

You do not need five ETFs to be diversified. One well-chosen broad-market ETF achieves more diversification than most people’s entire portfolios.

Common Mistakes When Choosing ETFs

Choosing based on recent performance. An ETF that returned 40% last year is not necessarily a good choice — it might be concentrated in a sector that happened to do well. Past performance does not predict future returns.

Overcomplicating with too many ETFs. Three broad ETFs (global stocks, emerging markets, bonds) is more than enough for most investors. Ten ETFs with overlapping holdings does not improve diversification — it just makes your portfolio harder to manage.

Ignoring currency exposure. When you buy a global ETF through a Thai broker, you are exposed to currency movements (Baht vs Dollar vs Euro). This is normal and generally evens out over long periods. Do not hedge currency risk unless you have a specific short-term need.

Confusing the provider with the product. Vanguard, iShares, and Amundi all offer ETFs tracking the same indices. The differences between providers are usually tiny — focus on the index, fee, and structure, not the brand name.

Key Takeaways

What the ETF tracks (the index) is the most important decision
Keep costs low — under 0.30% TER for broad market exposure
Choose funds with at least $100 million in assets
Ireland-domiciled UCITS ETFs are generally most tax-efficient for non-US investors
Accumulating ETFs are better for long-term wealth building
One well-chosen broad-market ETF is a complete equity portfolio

Frequently Asked Questions

Can I buy international ETFs through a Thai broker? Yes. Most major Thai brokers offer access to international markets — either directly (through global trading platforms) or indirectly (through DR/DRx, which are Thai-listed securities representing international ETFs). Check your broker’s international product offering. → Broker Comparison

Is it better to buy one global ETF or several regional ones? For simplicity and cost: one global ETF. For customisation (e.g., overweighting emerging markets or excluding certain regions): several regional ETFs. The global option is simpler and sufficient for most investors.

How often should I review my ETF selection? Rarely. If you have chosen a broad, low-cost ETF, there is little reason to change it. Review once a year — and only switch if there is a material reason (fund closure, significant fee increase, or a change in your investment goals). Do not switch based on short-term performance.