if your applying via the London embassy evisa site, different visa but I got asked to show proof of inbound and outbound tickets, to make things easier I booked a cheap onward flight to Cambodia for 90 days after my arrival. Then just didn't get on the flight, my UK return ticket is for 1 year after arrival,
I done my visa on London embassy website, I had to go into my computers album options and click collage it allows you put multi forms into one and send as a single document,
reason I chose to do online in London was due to many visa exempt entries already so arriving with a visa is a more viable option for me, but as tod said you have to decide what option is best for you.
I just did my ed visa in London embassy online, had my thai school email me the paperwork from school and ministry of education, got my visa approved within 48hrs.
You need 1 passport photo for visa on entry into laos but I was there 2 weeks ago. Many people didn't have photo but still got visa they just wanted your money. If you plan on getting a Thai visa while there you need 2 passports photos also.