score:2
First issue, your POOT (proof of onward travel) will be checked by the airline when you check in in Europe and without it, they likely will not let you board. End of trip. You need to be able to show that you are leaving Thailand to fly there under Visa Exemption rules. And for most airlines the only acceptable POOT is an airline ticket (bus or train tickets do not count). You might explore options for a cheap air ticket somewhere out of Thailand as a throw away or actually use it to get somewhere you want to go. Or get a fully refundable ticket and cash it back in once you are in Thailand.
You also could look at a tourist visa, which gives you a sixty day stay and airlines usually don't check for POOT. Right now (until 28 Feb 2017) single entry tourist visas are free.
Overland entries under the Visa Exemption program are now back to 30 days for all countries that qualify for VE, but there is a new rule limiting you to two overland entries per year.
Upvote:2
@Tom is correct about the real possibility of being unable to board in your home country or EU area on Visa Exempt (VE) entry to Thailand without POOT. You could use FlyOnwards.com to book a real onward ticket for $10 USD.
You can theoretically have unlimited VE entries via air, but land borders you can only have 2 VE entries maximum per calendar year. With your current strategy, you will be using 1 out of 2 VE land entries. If you wish to save that for another time, you could opt to obtain a Single Entry Tourist Visas (SETV) in Laos.
The free SETV scheme has been extended until August, 2017. But recent trip reports are that the nearby Thai Embassies/official Consulates such as Penang (Malaysia), Vientiane, and Savannakhet (Laos) have begun requesting bank statement summary pages that show you have THB 20k equivalent (can be non-thai bank) and proof of onward travel from Thailand prior to accepting the application. I am unsure if these extra requirements will be permanent process, or just temporary crackdown.