Should I use a blue pen or a black pen for my immigration forms in Thailand?

Most commenters agree that you should use a blue pen for filling out immigration forms in Thailand. The consensus is that using blue ink helps to indicate that the documents are original and not photocopies. However, there are anecdotal experiences suggesting that some immigration offices may accept black ink, notably in Patong, which had mixed reactions to ink color. Overall, using a blue pen is strongly advised to avoid any issues during the application process.