Tours in Laos in April are experiencing two simultaneous downturns. Tourist and price. And it is connected, because during the heat wave fewer guests come to the country, and hotels and stores immediately respond to this. So the prices for vacations in Laos in April are not high at all. You can find options up to 1000 USD for a sightseeing tour, excluding trips to Thailand and Vietnam.
Laos vacations in spring are associated with excursions to major cities like Vientiane or Luang Prabang, more than anything else. These cities happily welcome tourists all year round. You can visit Kaison Phomvihane (formerly called Savannakhet, and many people still call it that).
It will be quite feasible to visit Thakhaek as well, to walk in its clubs and see its temples. There are plenty of attractions near the city. Overall, if you are not intimidated by the heat and sun, this is not a bad time to travel.
Prices for tours to Laos in April range around 1300 USD for sightseeing programs in the central cities. If you don't know which cities and resorts you can go to for your budget, use the tripmydream service. It will find the most favorable tours to Laos in spring.