I'm pregnant with my third baby at age 37. Ten and nine years ago Had two normal pregnancies with no complications (full term; 38 weeks). My current pregnancy has no complications, but I have mild spider and varicose veins. I use 15-20mmHg compression socks.

At week 29 (then coming back at 32 weeks) I'm planning to travel overseas but the flight is somewhat long. Probably it will take including stopovers about 27 hours. I think the longest one flight would be around 11 hours.

What is your recommendation? Is it safe for me and baby?

Anyone pregnant at 37 should be in close communication with her OB team.
Make a list before asking:
destination country and city/town, with good idea of medical options there
type of aircraft, first class or coach, and how much walking room there is
types of unusual parasites or viruses known where you are going
cancellation insurance and what it covers
latest date you can assess your situation with your doctor

(I wouldn't go, but that's not based on anything but personal caution!)

To add to what Joy said, pregnant women are at increased risk for DVT's. Flights this long increase that risk even more.

This is is really a question you need to discuss with your OB since he/she knows your personal history. You also may want to contact the airline to see if they fly women at 32 or more weeks.