How many locations would you recommend for 10 days?

My girlfriend and I are travelling to Thailand for the first time April 30 to May 10, 2025. So far we've been thinking of doing:

• Apr 30: Land in Bangkok at 11:00 PM
• May 1: Bangkok
• May 2: Bangkok
• May 3: Catch night bus + ferry to Koh Sumai
• May 4: Arrive in Koh Sumai following morning
• May 5: Koh Sumai
• May 6: Koh Sumai
• May 7: Fly to Chiang Mai at 8:55 AM – 10:40 AM
• May 8: Chiang Mai
• May 9: Chiang Mai
• May 10: Fly back to Bangkok at 11:55 AM – 1:20 PM ($41)
• May 10: Fly back to Canada at 7:00 PM

Do ya'll think this is doing too much? Do you think we'll feel rushed with this itinerary or is it a good balance? I've been trying to convince my girlfriend to drop either Chiang Mai or Koh Sumai.

Alternatively, we could also do:

• Apr 30: Land in Bangkok at 11:00 PM
• May 1: Bangkok
• May 2: Bangkok
• May 3: Bangkok
• May 4: Catch night bus + ferry to Koh Sumai
• May 5: Arrive in Koh Sumai following morning
• May 6: Koh Sumai
• May 7: Fly to Bangkok at 7:00 PM ($112)
• May 8: Bangkok (Riverside)
• May 9: Bangkok (Riverside)
• May 10: Fly back to Canada at 7:00 PM

I'd love to hear what you guys think.