Long story short we bought about 17000 GBP worth of cheques mostly in 100 GBP amounts. We did this because it was cheaper than any other form of transfer between countries. We bought when the cost to cash them in Thailand was 30 THB per cheque. About a month later it rose to 150 THB per cheque which makes the total cost to cash them about 26,000 THB, instead of the 5200 THB it would have been. So a difference of about 20,000 THB.

My question is, in financial terms, is it worth going to a neighbouring country with lower cash-in fees? I've just had a quick look at fees at Maybank in Malaysia:

Encashment by tourist
Commission: RM10 per transaction
Stamp duty: RM0.15 per cheque (if applicable)

If I understand that right it'd work out to be about 400 THB to cash all of them.

But then there is the exchange rate between the Ringitt and the Baht when you bring the money back into Thailand, which isn't going to be favourable, right? How much of a loss can be expected there? Plus I'm guessing there are some sort of restrictions/risks when bringing that amount of cash through a land border into Thailand - is it possible if you have proof where the funds came from? I have a Malaysia bank account so possibly deposit the money from the cashed cheques in that and then withdraw it in Thailand?

It's a total backward mess, I know, but we had no idea the cost to cash in Thailand would x5 overnight when we bought the cheques.

One other question, do TCs have to be cashed to the local currency, or can you cash them in Malaysia in exchange for THB, for example?