McDonalds do provide 24 hours delivery service to selected areas in Thailand. The number to call is 1711.
You may view the brochure below as of June 2019 (click on the brochure image to enlarge):


I am not sure in Thailand but in Malaysia, the delivery service offered by fast food chains like McDonalds, KFC, Dominos covers a large area and is doing very well. We would usually call for delivery service when we have team meetings, gatherings or celebrating birthdays of staff.
Given the constant jam in Bangkok area, it would be more viable to just place a delivery order and just pay the 40 baht delivery charge than to go out, drive or even walk to buy for a group of people.
The conditions as stated in McDonalds Thai delivery brochure:
- No minimum order required
- 40 baht delivery charges
- For delivery at participating stores only
- All prices are inclusive of VAT
- Prices and menu can be different from each branch
- McDonalds reserves the right to change prices, menu, service areas and service hours without prior notice.
- McDonalds reserves the right to select the chicken pieces
- Cannot be used in conjunction with Ronald’s/McDonald’s club and any othe promotions
- Please allow 2 hours in advance for order 1000 baht and up
- The visual are for advertising only
Contact details:
Twitter: mcthai
Facebook: mcdonalds
Line: mcdonalds.th
Instagram: mcdonaldsthailand
Website: mcdonalds.co.th