How do you Write Merry Christmas in Thai?

There isn't a direct translation for "Merry Christmas" in Thai. Instead, you would say:

สุขสันต์วันคริสต์มาส (sùk sǎn wǎn khríst mǎːs)

This literally translates to "Happy Christmas Day".

You can also say:

* คริสต์มาสต์สุขสันต์ (khríst mǎːst sùk sǎn) - "Happy Christmas"

* ขอให้คุณมีความสุขในวันคริสต์มาส (kʰɔː hǎj khun mī khwǎːm sùk nǎj wǎn khríst mǎːs) - "Wishing you happiness on Christmas Day"

These are all common ways to wish someone a Merry Christmas in Thai.