@Simona **********
if you husband already has a Non Immigrant B visa and this is running to the end, he can apply at your local Immigration Office for 1 year Extension of Stay based on working inside Thailand. And if you already have the Non Immigrant O visa, you can apply the same day at your local Immigration Office for the 1 year Extension of Stay based on being dependent of being a family member of an alien permitted a temporary stay in the Kingdom. No need to travel to foreign countries and all can be done in one morning or afternoon.