eVisa (electronic visa). A real visa application, made online instead of at an embassy. It is assessed, it takes days rather than minutes, and it can be refused.
You apply online before you travel and are approved before you fly. There is no embassy appointment and no interview — you fill in a form on the government's own site, pay the government's fee, and carry the approval with you.
Status
eVisa
Stay permitted
A single-entry tourist visa is valid for 3 months from issue, and a multiple-entry one for 6 months. Each entry allows a stay of up to 60 days, which can be extended once by 30 days. (Royal Thai Embassy, Washington DC)
Changing planes: a passport from Nigeria needs a visa even to stay
airside in United Kingdom and Schengen area airports, unless you hold an exempting
document. Transit ruleslegislation.gov.uk · read eur-lex.europa.eu · read
What Thailand asks for
Passport biodata page, with the passport valid for at least 6 months from travel
A photo of the applicant taken within the past six months
Proof of where you currently live, such as a driver's licence, bank statement or proof of stay
Flight itinerary into and out of Thailand
Proof of accommodation in Thailand, such as a booking or an invitation letter
The Thailand Digital Arrival Card (TDAC) is free. You file it only at tdac.immigration.go.th, within 3 days before you arrive. Any site that asks for payment is not the Immigration Bureau.
Every traveller must file the TDAC on each entry, whatever their visa type and even if they are visa-exempt. It is not a visa.
Thai e-Visa applications are made and paid for only at thaievisa.go.th. The visa fee is non-refundable, even if the application is refused.
Details cannot be changed after you submit. The Abuja embassy says incorrect information, including a typing error, will lead to refusal.
How long it takes
Processing depends on the embassy that handles your application. The embassy in Abuja allows up to 10 working days and asks you to apply 4 to 6 weeks before you travel, and no more than 3 months ahead.