Was this an unusual landing sequence for an airliner? About a month ago I encountered an unusual landing during a flight from Bangkok to Krabi airport. We were flying Boeing 737.

We took off 30 minutes late. Our flight should've taken 90 minutes but it actually took less than 70 minutes so we arrived almost on time.

The seatbelt sign turned on around the 60th minute while we were still probably in 10000 meters (I don't know the cruising altitude for sure). The whole landing took less than 10 minutes. I guess the landing gear was deployed at around 6000 meters which seemed unusually high to me. The pilot also performed several rather sharp roll maneuvers and at one point he broke his descend and even entered a rather sharp climb. All this with landing gear out. I have to say that many passengers were quite terrified at the moment. The landing itself was hard but not that much.

I have been  wondering if it was a common maneuver (to decrease speed perhaps?) and would be interested to learn more about it. Does it have something to do with the flight speedup? How is it even possible to be so much faster on such a short flight?
Why do you think the flight "should" take 90 minutes?
You really mean it was listed for 90 minutes on the schedule.
Airlines almost always pad their scheduled times so that their on-time arrivals stats are favorable, and to account for normally expected delays.

Scheduled time is also typically measured "gate-to-gate", while most passengers only observe the flight-time (takeoff-to-landing)

I see the distance is 350 miles, and would probably take a 737 about 60 minutes of actual flight time.  So I don't think your flight was speeding or otherwise behaving abnormally.