Ho Chi Minh City is 5 hours ahead of Bucharest
Best overlap: 8:00 AM to 1:00 PM in Bucharest is 1:00 PM to 6:00 PM in Ho Chi Minh City.
Your shared working hours run 8:00 AM to 1:00 PM in Bucharest (1:00 PM to 6:00 PM in Ho Chi Minh City). You've got a decent 5-hour window. Set a recurring time near 8:00 AM in Bucharest (1:00 PM in Ho Chi Minh City) and stick to it. Watch the DST gap — when Bucharest changes its clocks and Ho Chi Minh City stays the same, this window slides by an hour.