Bjorn had six birdies and a bogey in his first round and is ahead by one stroke but about half the field was unable to complete first-round play due to rain.
Tournament organizers said play would resume at 7:30 a.m. Friday. Last year's Singapore Classic was also hampered by weather and reduced to a 54-hole event. This year's tournament is still set for 72 holes, however.
Bjorn started on the back nine of the Sentosa Golf Club and opened with a birdie. He added a birdie at 16 in making the turn at 2-under.
He birdied the No. 1 hole but suffered his lone bogey of the day at the third hole. He answered that with back-to-back birdies at Nos. 4 and 5 and used a birdie at the par-3 eighth to get to 5-under.
Khan had two bogeys -- and a birdie -- in his final three holes Thursday while Phadungsil also had a late bogey in slipping behind Bjorn. Martin had three consecutive early birdies but also had two bogeys in a three-hole span en route to his 67.