If you are a citizen of more than one country (excluding Thailand), you are still eligible for the Thailand Privilege Visa. To apply you will need to choose at least one passport you will be using for the application. You will be using that passport to enter and exit Thailand.

However, there are some details to keep in mind:

• If one nationality is on the restricted countries list, but your other nationality isn’t, you will need to use your passport from the nationality not on the list to apply for the Thai Privilege Visa. 
• Some nationalities are not visa exempt. If you decide to use a passport from a non-visa exempt country, you will need to apply for the Thai Privilege Visa outside Thailand and acquire the visa sticker at the Thai embassy or Royal Thai Consulate located in that country. 
• The passport you use will need to be valid for at least 12 months (365 days) or more upon submitting it for the application.