Sorry to hear about this . This is the major pitfall of a long distance relationship , the first thing I would do is cut the funding completely, I don’t mean for one month I mean for ever until you get a dna test! once it’s confirmed you get a British passport for her . As soon as that’s done you save that money that you have not be sending her and you give her a one time payment to stay out of your life forever she will happily take it . take your daughter and bring her up in the UK . 

To add once you cut the funding she will surface like a cockroach especially when they are both clucking for another hit . Use her addiction to your advantage be cold hearted but remember your daughter could end up being the family’s future hooker if you don’t get her out of there . It’s harsh words but true mate . 

I must thank the OP for publishing his plight, it could serve as a warning

to newbies considering a Thai lady wife, although the UK is just as fraught

with catastrophies, as most of us have experienced.

Best to choose an ugly woman with a beautiful nature, and you've cracked it.

 

Dont look back look forward and make a plan. When the money runs out she will contact you or be forced to by the others who benefited from you sending money when she contacts be ready with money for taking your daughter back with you but dont send any money until you have a list of demands and not just her promise for this and that. Tell her as soon as you have some sort  of  legal custody you not will not be sending money. Make arrangements to meet her at a lawyers and buy your daughter back sad as it seems this is Thailand and money talks 

Thai girl. Met in a bar. Works as a masseuse. That right there are three huge red flags!

 

Kidding aside, sorry to hear about your situation. There's really not much you can do unfortunately, unless she wants you to take custody of your daughter. But she would most likely rather use your daughter to milk money from you in the future. That's the only leverage she has, and she sounds like a real piece of <deleted>.

I'm a bit late on this, but I feel The OP is being a little harsh in calling it a "scam".  It sounds more like a fairly normal breakdown of a long-distance relationship.  Presumably there was no evidence of a drug addiction while she was with you in Thailand or the UK?  Had the Settlement visa been processed, you would all be together now in the UK.  Sounds more like she was depressed at being apart from you, or frustrated at how long things were taking, and fell into recreational drug use and a "tomboy" relationship. Both are not uncommon, and are easily finished, unless it's something like heroin that she's on.

 

I would fly out to Thailand at the earliest opportunity (admittedly not easy at the moment) and try to repair the relationship (assuming you want to), and if it's not possible divorce, which if you're both consenting, is easy.  Unfortunately, your daughter will be staying with Mum, unless the drug addiction is very serious.

 

Good luck.