In line with many countries (including USA, Australia, UK), Thailand is to phase in new restrictions on what passengers travelling by air can take in their hand baggage when travelling from Thai airports. There has already been some confusion, but I’ll indicate what the rules are supposed to be.
Liquids, aerosols and gels being carried in hand baggage need to be packed in a transparent, resealable plastic bag and kept available for inspection by security staff at the airport. Only one such plastic bag will be allowed. Individual items within the bag should not exceed 100ml with the maximum total being 1 litre. It is the passenger’s responsibility to provide the bag.
There are exceptions on the above limits for dietary/medical/baby requirements, but these items should still be placed in a clear, resealable bag.
As I say, these are supposed to be the new regulations being introduced this month. I’m not sure whether bottles of water are being allowed (probably not), but water will be provided on the plane.
If in doubt, put your toiletries in your checked baggage.