As someone as posted already, ensure any wording in any document says "Parental Power" - that is what carries the weight, not the word 'custody'. Because my ex knew that our child would be better off with me in the west, it was an easy process. No arguments at all. However, note that if you get 100% parental control, it would only be applicable in Thailand. 'The west' takes more of an equitable view, and unless there was abuse / violence happening, would not accept 100% control by one parent. In this respect, I actually have more power in Thailand than I do in UK! But, no problems with 'mum' as she's supportive of our plans.