I'm going to chiang mai too but it's on the november for 1 month. I fly with scoot for about 400 sgd.
Chiang mai is really A wonderful place to visit.
Many place worth visiting! Most people that go to chiang mai usually go to the place you mentioned.
It's better to do A camping if you are going to Doi Inthanon for the best view. If not no point going there.
For shopping mall there are a few recommandation
1. Central Airport Plaza
2. Maya Lifestyle Shopping Center (Plenty of female stuff)
3. Central Festival (Selling branded stuff)
If you are going to bangkok. It's more convinent to move around compare to chiang mai.
1.Skytrain (MRT)
2. Tuk Tuk
3. Taxi
4. Grab
Always remember to ask them to open the meter for taxi before boarding or you will face overcharge price given by them. Don't ask them to recommand you place to eat because they will bring you to restaurant that charge high price. Tuk tuk overcharge too ! And they might ask you to help them by sending you to shop and ask you go take a look in the shop. Because they will get coupon for their fuel by sending people to the shop.
There are many places I want to introduce to you and show you some picture but It seems that I can't upload here xD
$400 can fly Silkair...
