I would like to book a flight online from Chiang Mai to Bangkok for my girlfriend with my Credit Card.

I will not be travelling with her. Seems like most airlines will not accept this. They need to see the credit card that paid the bill.

Are there any that will?

The first question we ask back is ... which Airline?

When I book tickets for one of my family to travel, without being accompanied by me & my credit-card, I give them a signed-photocopy of the card (both sides) and something like "I, NAME the cardholder, have authorized my card to be used to to purchase the following flight-tickets ... for XYZ". That certainly satisfies some airlines.

Alternatively, if you're within the country, book the ticket & pay cash at 7/11 or Tesco-Lotus or wherever, so that she can just quote the 6-digit reference-number, at check-in ?

Or perhaps send her the money by bank-transfer or in cash ?

The credit-hard-holder not-accompanying seems more of a problem for last-minute purchases, IME.

Air Asia, can do.

No problems with Thai Air Asia.

Have done this for my wife several times for flights from Bangkok to Ubon Ratchathani.

I check her in online then email the PDF boarding pass for her to print.

They have never asked to see the booking invoice let alone my credit card details.

No problems on Nok Air nor Air Asia, have booked for others many times with never a question about original credit card being present.

Thai Air seems to be the one that is a real stickler about this

Nok Air, Air Asia no problems for this from experience.

Yes, Thai Airl used to have an online authorization form that could be filled and signed by the cardholder and sent to the passenger as authorization, I did this several times. Now the Website says:

Consent Form regulations New Regulations for passengers who are not Credit Card or Visa/MasterCard debit card owners:

You can sponsor an electronic ticket to anyone upon payment, following the below instructions, which is strictly recommended.

1. Credit Card or Visa / MasterCard debit card owners must contact any THAI city ticketing offices only during office hour at their nearest locality in person and present the following documents;

• Credit Cards or Visa / MasterCard debit card used in the purchase
• ID or passport matching that of the owner of the credit card
• Completed and signed Consent Form.

2. After the documents have been verified and approved, THAI shall provide you booking reference.

3. THAI reserves the right to deny boarding to the travelling passengers, if the above mentioned procedures and regulations have not been complied with.

I have booked with Bangkok Air, Orient Thai, Air Asia and Nok Air for other people with my credit card. Never a problem. Bangkok Air used to have a policy that the owner of the card had to fly but this changed last year.