I kicked started my wife's mother's funeral with 20,000 baht. After the first day the donations kept it going 4 more days. The cremation day was the biggest payday. Set back and just let it happen. The less you are involved the better. As this is your girlfriend's family, If by chance you are asked to donate more it's only for show. The look at us, we are highso. The funeral will proceed with or without a big show of importance on the family's part.