Bangkok gets all dressed up for Christmas, loads of decorations, Christmas music and (fake) Christmas trees. Certainly other parts of Thailand participate with decorations and such, especially the towns and cities that are tourist destinations.
But Christmas is not a national or government holiday, it’s business as usual in Christmas eve and day. Of course many westerners take the day off, but Thai workers do not and all banks and offices are open.
Thais seem to like Christmas, they enjoy anything fun. Christmas observance in Thailand has nothing to do with religion, just a chance to put up some decorations, wear funny red hats and shop. And Thais love to say “Merry Christmas” to all far angus on Christmas day, always makes me smile.