According to the ThaiEmbassy.com website, a farang who wants to become a Thai Citizen will first need to be a Thai Permanent Resident for 10 consecutive years. In order to get a Thai Permanent Resident, you need a Thai non-immigrant visa for at least consecutive 3 years. Multiple Non-immigrant visas cannot apply. See the link to the Thai Embassy website for the full requirements.
Once you have the Thai Permanent Resident and have lived in Thailand for 10 consecutive years, then you can apply for Thai citizenship.
To qualify to apply for Thai citizenship, the applicant must meet the following criteria: – See more info
If you think you qualify, you may apply to be a Thai citizen but there is no guarantee.
I don’t think you need a lawyer to do all of this for you, unless you have the cash and need someone to hold your hand. If you can read, follow instructions, you can do everything yourself.
I don’t know any farang that has got this far. I only read of someone who claimed to do this and it took him 3-4 years to become a Thai Citizen.
If you’re a farang, and you haven’t lived in Thailand for 10 consecutive years, or you don’t speak Thai, just forget about it, they don’t just hand them out to anyone.
I think it’s probably the only thing in Thailand you cannot buy.
Requirements to get a Thai citizen for foreigners
Step #1 (Get your Thai Permanent Resident)
Live in Thailand for at least 3 consecutive years with a Thai non-immigrant visa. Multiple Non-immigrant visas cannot apply. See link here for more info.
Step #2 (Apply for Thai Citizenship)
Once you have the Thai Permanent Resident and have lived in Thailand for 10 consecutive years, then you can apply for Thai citizenship. See link here for more info.
I cannot guarantee the accuracy of the links provided and I cannot guarantee anyone that applies will become a Thai citizen. Use the information at your own risk.