Found that there is nothing much to see in Vientiane and I asked the hotel to refund the second night room charge. The lady said the hotel has to pay Agoda S$2.87 as I have booked 2 nights online. I paid for the fine and get back the balance S$10.98 to buy the bus ticket to Viang Vieng. I paid S$8.44 for a VIP bus but I guess there were not enough people to fill the bus and the 9 of us were directed to take the mini van. The journey from Vientiane to Vang Vieng is about 3.5 hours.  

Vang Vieng a lovely place and my 2 days of visit was worth every cent of it. The city is rather small but there are some adventurous things to do, like rafting in the river, tubing through the water cave, kayaking in the blue lagoon, taking hot air balloon ride, trekking into the dark caves, walking along the street with shops on both sides and others.

I got the day trip for tubing, kayaking, trekking and visiting the caves from a small travel agency set-up along the road. Later I realised that I should get the ticket from the organising company directly instead of from the hotel or the road side tour agent as they do mark-up the prices.