When I moved to Thailand in 2005, the pound was getting you around 72 baht. I remember it clearly because I was living off a UK salary converted into baht, and every trip to the ATM felt like a small win.

A cold Chang on the beach in Krabi cost 40 baht. That's 56p in real money. You could spend an afternoon drinking on a tropical beach for the price of a Mars bar back home.

Twenty years on, the pound buys about 43 baht. That same beach beer costs around 120 baht. So in sterling, what used to cost 56p now costs about £2.76.

Your beer got five times more expensive. And almost nobody can tell you why.

This is the Beer Index. It's the most honest exchange rate calculator in the world, because it bakes in the two things that actually decide what your money is worth abroad: the FX rate, and local inflation. Most people only think about the first one. The second one is doing more damage than they realise.

Let's break it down

The five-times increase is not one thing. It is two things multiplying together.

First, the FX move. The pound has weakened against the baht by roughly 40% over twenty years. In 2005 your £1 bought 72 baht. Today it buys 43. That's a serious erosion of buying power, and it's not random. Thailand ran current account surpluses for most of that period, built up enormous foreign reserves, and the baht quietly became one of the more resilient emerging market currencies in Asia. Meanwhile sterling did sterling things: Brexit, inflation shocks, a mini-budget that briefly turned the pound into a punchline.

Second, Thai inflation. A beach beer tripled in baht terms, from 40 to 120. That's not greedy bar owners. That's twenty years of compounding cost pressure on imported barley, local labour, beachfront rent, tourist demand, and the Thai government tax regime on alcohol, which has been hiked multiple times.

Multiply the two together. The pound bought 40% fewer baht, and each baht bought a third less beer. Your sterling buying power on that specific beach, for that specific beer, has fallen by about 80%.

That is the Beer Index doing its job.

Why this matters beyond beer

If you are sending money to Thailand, retiring there, running a business there, or just planning a holiday, the headline FX rate on your banking app is lying to you by omission. It tells you the conversion. It doesn't tell you what that conversion actually buys on the ground.

Two countries can have a stable currency pair for a decade and the cost of living gap can still completely reshape itself, because inflation rates diverge. Thailand's official inflation has averaged around 2% a year for the past two decades. The UK's has been similar on paper, but anyone who has bought a pint, a train ticket, or a house in Britain knows the lived inflation is something else entirely. The two countries are inflating in different directions on different things, and FX rates only partially correct for it.

The Beer Index strips all that out. One product. One country. One purchase you actually make. It tells you the truth about your money.

The beer is the constant, the currency is the variable

This is the bit I think most people miss. A beer on a Thai beach in 2005 and a beer on the same beach today are essentially the same product. The label might be different, the bar might have nicer chairs, but it's the same transaction. Cold lager, plastic table, view of the Andaman.

What changed is everything around it. The pound got weaker. The baht held its ground. Thai prices crept up. British wages didn't keep pace with British inflation. And so the same beer, which cost a Brit 56p in 2005, now costs the same Brit nearly three quid.

If you'd held that 56p in cash for twenty years, you'd still have 56p. If you'd held it in a UK savings account at average rates, you'd have maybe 90p. If you'd held it in baht, you'd have around £1, with no growth, just from the FX move. None of those gets you a beer on the beach today.

This is the part of personal finance nobody teaches you. It's not just about saving and investing. It's about what your money can actually do, in the place you actually want to spend it, at the time you actually want to spend it.

How to use the Beer Index for your own planning

If you are a saver thinking about retiring or spending time in Thailand, run the Beer Index on the things you care about. Not just beer. Pad thai. A taxi to the airport. A month's rent in Hua Hin. A medical check-up in Bangkok.

Track them in baht. Track them in pounds. Watch how the gap changes over time. You will learn more about your actual buying power in five minutes of that exercise than in a year of staring at the GBP/THB chart.

The exchange rate is a snapshot. The Beer Index is the film.

And right now, the film is telling us that a Brit's money in Thailand isn't quite the superpower it used to be. It's still good. Thailand is still cheap relative to the UK on most measures. But the gap is closing, year by year, beer by beer, and anyone planning a future there should know that.

Mine's a Chang. Just don't ask me how much it cost.