How to track cash spending in Thailand, Bali and Vietnam

A card leaves a trail. Every tap is a line in someone's database, waiting to be summed at the end of the month whether you remember the purchase or not. Cash leaves nothing. It slips out of your wallet at the food stall, the scooter rental and the temple donation box, and unless you write it down in the moment it is simply gone — a hole in the ledger you can feel but never quite account for. And in Thailand, Bali and Vietnam, cash is most of what you spend. These are the three places a long-stay traveler is most likely to lose the thread, partly because the spending is fast and small and constant, and partly because the currencies themselves are designed to confuse a newcomer. Here is how each one works, and the single habit that keeps all three honest.

Thailand: the baht, and why it's the easy one

Of the three, Thailand is the gentle introduction. The baht (THB) behaves the way Western money does — prices are quoted in whole baht, and the numbers stay small enough to hold in your head. A street coffee is 45 baht, a plate of pad kra pao maybe 60, a longer songthaew ride 30. There is a subunit, the satang, but you'll almost never meet it; everything rounds to whole baht in daily life. The split is simple too: cash for the things that make Thailand worth being in — street food, the morning market, the songthaew, the 7-Eleven snack — and a card in the air-conditioned malls and supermarkets when you want it. Because the figures are intuitive and the decimals don't bite, Thailand is the easiest of the three to keep an honest tally on. If you can build the logging habit here, the other two are just bigger numbers.

Bali: rupiah, and the ribu trap

Bali raises the difficulty by adding zeros. The Indonesian rupiah (IDR) deals in large numbers — a meal at a warung lands somewhere between 50,000 and 150,000 rupiah — and the first few days your brain refuses to parse them. The locals long ago stopped saying the zeros out loud. A vendor who tells you the price is "50 ribu" means 50,000, ribu being the word for thousand; menus and signs do the same shorthand, so "50k" and "50.000" both mean the same fifty-thousand-rupiah plate. The trap is exactly there: glance too fast and a 150,000 dinner reads as 15,000, or you fumble a note and overpay a zero's worth. Cash is unambiguously king for the things you actually do in Bali — the warung, the scooter rental and its tank of petrol, the market haul of fruit and sarongs — so the rupiah is where most of your money lives and where most of your tracking errors will hide. Hear it as "ribu", write down the full number.

Vietnam: the dong, and the most zeros of all

Vietnam takes the rupiah's problem and adds another zero on top. The dong (VND) carries more of them than any currency you're likely to handle on this trip: a short Grab ride across town is around 82,000, and you'll see it written "82k" on the app and in shop windows. Coins have effectively disappeared, so every price you touch is already in the thousands, paid in worn paper notes that look unnervingly similar across denominations. This is where the single most expensive mistake in Southeast Asia happens — misreading one zero. The difference between 82,000 and 820,000 dong is the difference between a three-dollar fare and a thirty-dollar one, and the difference between a 5 and a 50 in your end-of-month total. The dong rewards exactly one discipline: write the number down the instant you pay, before the zeros have a chance to rearrange themselves in your memory.

The ten-second habit that works everywhere

The fix is the same in all three countries, and it is almost embarrassingly simple: log each expense in the moment, in the currency you actually paid, in plain language. The moment matters because cash has no paper trail to reconstruct from — if you wait until evening you'll have forgotten the temple donation and rounded the lunch. The currency matters because the worst thing you can do is convert in your head at the cart. Doing arithmetic at a fluctuating rate while a vendor waits guarantees errors, and those errors compound silently all month. So don't. Write "coffee 45 baht", write "warung 80 ribu", write "grab 82k dong" — the raw amount, the real currency, a word for what it was — and keep a running balance per currency. Ten seconds, standing right there. That's the whole method; everything else is bookkeeping.

Keep one honest total

Three running balances in three currencies is the honest way to live day to day, but eventually you want the single number — what did this month actually cost. Convert to one currency only at that point, when you need the big picture, and use the daily mid-market rate so the figure means something rather than the marked-up rate a money changer would have given you. Doing the conversion once, deliberately, at the end is both more accurate and far less work than guessing forty times at forty food stalls. When tax season or a budget review comes around, export the lot to CSV and the whole trip lays itself out in rows you can sort, filter and total without retyping a thing.

This is the workflow ExpenseAI was built around. You type a sentence — "coffee 45 baht", "grab 82k dong" — and it detects the currency, reads the amount and files the category in the time it takes to pocket your change. It handles THB, IDR, VND, PHP, MYR and USD natively, keeps a running balance in each, and never asks to connect your bank, because no bank can see the cash you spend here anyway. There's a free tier; Premium adds budgets, CSV export and trend charts. For the currencies in depth, see our guide to Southeast Asian currencies; for the habit in full, the full cash-tracking method; and if you're still choosing a tool, our roundup of the best expense apps for the region.

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