@Lun ****
Nothing. Passport only. Far less mask wearing in Laos than in Thailand, generally speaking. No need to wear a mask anywhere and hardly anyone does anyway. Immigration officials being a possible exception aside, you'll see plenty of smiling faces whether you walk into a convenience store, hotel, restaurant etc as none will be wearing masks. Thai consulate clerks probably will be though! They are still living in fear but Laotians haven't been subjected to the fear porn that Thais have been hence the difference.