I just hear that since a few days we have a new bus connection from Khon Kaen to Vientiane, Laos

Leaves from "Air" bus terminal at 08.15. Only stops at the border. Farang must have visa to Lao to go on the bus. Thai must have passport or 3 day permit.

The trip takes about 3 hours. Price for a single ticket: 180 THB.

I have used this bus service many times. It is quite an efficient way to between Khon Kaen and Vientiane. The cost varies slightly with a 5 Baht surcharge on weekends.

Last time I used the service there were two busses a day each way. Travel time about 4 1/2 hours. The departure times were 08:15 and 15:15 (at both end of the journey) but varied from time to time requiring a check before heading off to start the journey.

Does anyone have up-to-date info on the departure times?

Concerning the requirement for a Lao visa: the bus will not wait for you while you apply and obtain a visa on arrival at Friendship Bridge. If you do not have a Lao visa, you can still take the bus, but get off at the Lao border passport control, making sure you take all your bags. Then apply and pay for your visa (USD30) and take the shuttle bus from the border to Vientiane (or take a tuk tuk).