Can my friends from Sweden do a border run with a one month visa exemption for another month in Thailand?

Yes and yes.

1. Sweden are part of the 30 day visa except scheme (according to %20on%20Arrival/VOA.pdf). You can leave and return by land for another 30 days twice. You can also leave and return by air for an undisclosed unlimited amount of times. You may have to show 20K THB in cash if you use this method.

2. You can get a 60 day tourist visa before you leave. I highly recommend using this method if you are staying here less then 60 days.

Good luck.

also kindly note: Airlines are required by Thai Immigration to control whether passengers checking in for a flight to Thailand without any visa comply with all the requirements of Visa Exemption. Those include what is termed Proof Of Onward Travel (let's call it POOT) meaning a confirmed air ticket out of Thailand or a return flight home within 30 days of arrival. (Train tickets or plans to take the bus do not count, nor do domestic or international flights booked in other countries in the region that do not include a flight out of Thailand.) Airlines fear that failure to comply could result in severe penalties for the carrier and repatriation costs. Passengers who do not have POOT or a visa are at risk of being denied boarding. Airlines departing from Europe, USA, Canada and Australasia are reported to be more rigorous in applying this requirement than other regions. Regional carriers around Thailand hardly ever make an issue of it

Q1) Yes, but you can also extend for 30 days at immigration for 1900b.

If your friends want to stay longer, they can get a single entry tourist visa in Sweden (or from more or less any Thai embassy/consulate) and stay 60 days and then extend it for a further 30 days, also for 1900b

. .and yes your advice to get a Single Entry 60-day tourist visa right away from a consulate or embassy in Sweden is the better option. You can stay 60 days and can extend them for another 30 days inside the country, no need for a border hop. And the 1900 THB against the SETV visa fee is almost square

you can get two visa exempt entries per one calendar year when entering Thailand at land borders. You can make like 3-4 visa exempt entries through airports before they start to ask questions and doubt that you are a "real" tourist. You cannot extend the exempt-visa by a border run. You leave Thailand then the previous 30-day Visa Exempt becomes void. However you get a new one when you enter. Borders to Cambodia seem to hold on a stance that you need to spend 24hrs in Cambodia before you can return. However there is also the option - you can extend the 30-day Visa Exempt for another 30 days before it expires, at ANY immigration inside Thailand for a fee of 1900 THB