Both MRT Blue Line and Purple Line and BTS SkyTrain are extending their services on New Year from 6:00 am of December 31, 2017 to 2:00 am of January 1, 2018.
This is BTS announcement posted on its website.
“Such a wonderful ride! This New Year’s Eve, BTS is extending SkyTrain service hours from 06:00 hrs. on 31st Dec. until 02:00 hrs. on 1st Jan.”