That cute little temple is located in Ban Ving Keo near Hongsa and it is called Wat Vingkeo. The best way to visit is by motorcycle or bycicle which you can rent by some guesthouses in Hongsa and it will take you roughly half hour of moderate cycling to get there (depends on how often you'll turn into off beaten paths on your way or how often you'll stop for taking photos). It is really wonderful wat with many colorful wall paintings on the outer and inner walls; take your time to study each painting with its own story and you'll be busy for the whole afternoon (or day if you're really into details). Most of them are from local/Buddhist life. There is middle sized elephant sculpture next to wat made of black plastic bags - I believe it was made for elephant festival year prior to festival in Pak Lay. It's very nice and interesting.
You'll notice some quite large wooden houses for spirits in the temple's yard and some of them are big enough to shelter a novice. Like in other cases around Laos they were build when someone died. In the backyard you'll be able to see elongeated one and that one was specailly interesting as I never saw that kind of house for spririts before while visiting other temples around the country.
Wat Ving Keo is wonderful, magic kind of place.
Like in other remote towns there aren't much things to do after the sunset. There's no public light yet in the streets of Hongsa and most foreign visitors hang out in front of their guesthouses or some of the few restaurants in town which remain open - though not untill very late. Since there was international border crossing opened recently some tourists from Thailand choose Hongsa for their visa run and would stay only overnight. Apart from GHs and restaurants streets remain really quiet and dark. If you're lucky enough you'll see some of the local festivals in dry season and those can be really fun.
If you go to Xayabouli capital, you will have to take long ride (between 4 - 5 hrs if everything ok) by a pick up car. It leaves from market: there's small pick-up station and you have to buy a ticket before leaving. We were told to be there at 9 in the morning but it actually left Hongsa about 10.30. It means that pick up will leave when they have enough costumers and if you want to sit inside you must get there before others. Sitting in the back of the car on the open air means you'll have to swallow a lot of dust and be exposed to hot sun or rains and it certainly won't be comfortable as the trailer get full of passengers, rice bags and other bags, vegetables and animals and other things and thus squeezing your place to minimum.
Note that road to Sayabouli may not be passable in the rainy season since it's not paved.
Also if there won't be enough costumers some day in dry season, it may happen that driver won't want to leave and you'll have to wait another day. Hongsa is remote place and a road between Sayabouli and Hongsa hasn't yet been much travelled but if you do decide to take that way you'll pass some very nice hill-tribe villages and beautiful green mountains with spectacular views. By the way, as a foreigner you are expected to pay 120 000 KIP for that route, locals pay 80 000. Either way - it's expensive for that kind of ride.
Market is most obvious place to whatever shopping happens in Hongsa but your best buy will be probably fresh fruits for your trip and seeds. If you're handicraft buyer there are a few ladies of Hmong minority who sell their stuff for very reasonable price (specially if you compare same things with prices at Luang Prabang night market).
What to buy: minority shirts, silver, fruit, seeds
What to pay: all things are (very) cheap and don't be shy to pay a little bit more specially if you liked their service
Sarongs made in Hongsa (Ving Keo village) are trully piece of art. You'd hardly see more complex hand woven patterns on the black cotton background and it takes 5 days on average for skilled girl to finish her work per cloth. Traditionally they are made by Lue minority and there are many women who keep it doing nowsadays. You'll see them weaving by nearly every house in Ban Ving Keo and even very young girls are encouraged by their mums to do some. These sarongs are then sold mostly over the border to Thailand where they get quite good paid (on the other hand they would never know for real price since they're mostly collected by traders who come to the village). With that income women can support their families but also pay for education of their children. If you visit Ving Keo you'll see local women firsthand when weaving and if you want you can start negotiating for best price when work is done (and don't expect to pay less than 1000 THB for more simplier ones).
If you find yourself in Ving Keo village (and I am sure you will if you stay in Hongsa longer than a day) you will notice there is tobacco in front of almost every house. When it's ready they would cut it into very thin pieces and let it dry in the open air untill it gets completely dry. You can buy it fresh there - but keep in mind: it's very strong one and probably you won't need it very much for your own consumption and friends. It's cheap though...