My TW has to complete a tax return and I noticed that one question was if she was married and if so to a foreigner.

Just wondered the reason/need for this information and if there is any follow up by the tax office when "yes" is selected?

Does anything change?

You got more deductible if married

On a PND 91 tax return a tax payer can claim a 30,000 baht 'spouse allowance' as being married to a spouse with no income, or a spouse who combines their income with the the tax-payer and reports it jointly - basically reducing your taxable income by 30,000. You don't have to claim it, for example, if you don't want to show your marital status, but you'll lose out on a 30,000 baht credit. If you do claim it then you do have to report the spouses personal id number and tax id number (if they have one), their name, whether they have income or not, and how they report this income. Never seen a question about whether the spouse is a foreigner or not, and the allowance doesn't depend on spouse nationality. May be to do with the 'personal id number' request ?

Thanks, appreciate your comments.