BTS fanpage said on Saturday (May 16) that the expansion in service came after the Centre for Covid-19 Situation Administration announced on Friday (May 15) curfew hours will be reduced from 10pm to 4am to 11pm to 4am. 
Currently, trains run until 9.30pm. 
The Skytrain operator also said that the parking lots located near Mor Chit station will be available from 5am to 1am.

BTS trains to run until 10.30pm after curfew hours reduced

BTS train services will be available from Sunday (May 17) from 5.15am (Sukhumvit Line) and 5.30am (for Silom Line) until 10.30pm.