I'm pretty sure you don't have to see a doctor to get penicillin in Cambodia, I got some antibiotics from a nurse on Koh Rong. And pharmacy staff will definitely understand "penicillin".
Still, it might be a good idea to see a doctor anyway instead of self-diagnosing and self-medicating.
Best ask your hotel/hostel's staff, they should know a doctor who ...
While not exactly casual, there's an organization called "Learn Khmer Language - Siem Reap" that's specialized in teaching the Khmer language to foreigners. The organization seems to be active as of late 2016. Their fees per hour are:
4$ with a group of 3-4 people
5$ with a group of 2 people
8$ for individual
I believe $4 would be small enough ...
Another option would be to go through Thailand, take a bus from Pakse to Ubon Ratchathani (3 hours leaving 7:30 am).
From there take a bus to Surin running on highway 24, there may be a train (3 hours) as well.
From Surin you can take a swangthaew or minibus to the Cambodian border at Chong Jom (2-3 hours).
16 km south of the border is Along Veng but ...
It looks like that page I quoted on www.cambodiahome.com is at least out of date, and probably just outright wrong.
I asked the person at the desk at my guesthouse and it seems jpatokal and Tom are right that it can't be done directly in Siem Reap.
The guesthouse quoted me a price above $60 taking four days by sending it off to Phnom Penh.
I think I'll ...
From everything online (blogs, wikitravel, and websites) the ferry as you know is best in the wet season, when the river is high (June to November, usually)
However, as the dry season approaches or ends, it's debateable. If the rain comes early, you could be ok. However April is quite well into the dry season, but still over a month before the rains - it'...
What is still possible for tourists is to rent bicycles (basic ones go for $2-3/day, mountain bikes for $5-8).
Given the terrain (completely flat, pretty good roads, mostly shady) and distances (ca. 17km for the "small cycle", 28km for the "grand cycle"), that's actually a perfectly workable alternative, if you like to be physically active.
The midday ...
You left out some major information. If you are from Somalia or North Korea you are going to be waitng a looong time.
However, the Cambodian Visa can be done on arrival at the border if you are coming from Thailand. Many provate tour companies will do this process for you. I will warn you now, many tour companies will charge you extra money for the visa ...
I am a US citizen abd visited Siem Reap in December 2018. I got my visa on arrival. It took less than half hour. The process seemed very systematic and efficient. I carried a photograph for the application; I recommend that. Also carry US$30.
Hope this helps.
You should go to U-care pharmacy, they will have a doctor to consult your disease before you can purchase the medicine. You can find the U-care pharmacy of the East corner of Pub Street or another place along of Sivutha Street.
We have our own motorbike from Vietnam. No problems taking it into the Angkor Archeological Park. There are so many cars, tuk tuks, buses, motorbikes on site they would have a hard time only allowing registered vehicles, if that is even the case. As long as you have tickets for the park. We parked our bike in busy places like near food vendors.