Is a PhD obtained in the UK, US, or other western universities on the same level as one obtained from a Thai uni?

Come to think of it, what about a Masters degree? Same level here as in the UK? 

Poles apart ! To my knowledge paperwork here is only rated here, outside its pretty meaningless.(depending onthe  field)

Just take a look at the world ranking for the Universities.

Thailand is around 325th

 

https://roundranking.com/ranking/world-university-rankings.html#world-2021

Depends on the field and who your supervisors are tou can have both Thai and Western supervisors - I know one Thai student in Thailand who has both). You could be based in Thailand and doing data collection in the US or elsewhere. So the standard is up to what you produce in your PhD and what you publish thereafter (publish in English, of course, in high rated journals). The university is just the place where your office/lab is. 

PhDs are rarely the same level at two universities in the same country, let alone in different countries. Most USA PhDs aren't directly comparable to UK PhDs because in the UK we start to specialise much earlier, and USA HE tends to be broader for much longer. USA PhDs are largely taught courses rather than getting straight on with the research, which is why ABD is a thing in USA but doesn't make much sense in the UK. Most of the USA PhD theses I've read would be approximately equivalent to a master's dissertation in the UK. (That's not a criticism of USA programs, just that the two educational systems have different approaches and priorities. You can't compare them directly because they are aiming to do different things.)

But as DavisH says, none of it really matters. All anyone will ever care about is the resulting publications. If you come out of it publishing in good quality journals, no-one will care where you got the PhD from.

If i had a baht for every time this question was raised....
It varies of course.  Its not as bad as some here suggest but results will vary.  If you attend one of the strongest schools (Mahidol, Chulalongkorn, Thammasat, KMITT, etc) you would have no trouble with "recognition" of your degree.  Frankly speaking - the PhDs in Thailand have an extra layer of difficulty, in that beyond defending your dissertation - a peer reviewed academic journal article of your findings has to be published in a Scopus recognized peer review journal.  I would say that that requirement serves to bolster the graduate against claims of "inferior" quality. I am a doctoral level thesis advisor and have overseen 3 doctoral candiates so far.  All three and their research work are full comparible quaility to any in another country. Indeed, we have a requirement that there be international thesis examiners on their committees as another quality control mechanism. 

1 hour ago, MSMU1993 said:

 a peer reviewed academic journal article of your findings has to be published in a Scopus recognized peer review journal. 

Then I'd rate them higher than many US PhDs, especially in STEM subjects. The ability to get a PhD without the expectation/requirement for peer-reviewed publication is the main reason why US PhDs are considered to be a lower level than the UK or Australia. I needed two publications to be put forward for viva (which was an actual exam, not just a presentation), and the expectation was a minimum of 4.