Singapore - rescheduling.
 

We have booked SQ for our trip to BKK, but the 9th of January they noticed us that they had resceduled the CPH-SIN departure, which results in arriving at BKK about 3 hours later than planed.
Is there any EU regulations which considers rescheduling eligble for compensation?

There is no specific rule under 261/2004 about reschuduled flights ahead of time, it mostly deals with cancellations and delays. However, you do not have to accept the change and can demand a full refund. However, this often means that you will have to rebook with another airline at a higher fare, so I would be cautious about this option.