Definitely not the most spectacular display from the glorious Ahom dynasty and best combined with visits to other archaeological sites around the city of Sibsagar/Sivasagar. As mentioned in the other reviews, the necropolis are divided into 2 sites - Assam State and Archaeological Survey of India (ASI) thus separate fees. Each cost 250 rupees for foreigners and 20 for locals. There's a new visitor center at the Assam State controlled gate which has some information board that details the origin of the burial mounds, maps, and some info-graphics of the interiors which I think would be helpful how to tackle the site and to learn more about the history of the place. I wasn't asked for ticket at this point. The Charaideo poster photo of the mound with a restored arch gate and accessible interior (mound 38) can be found on the Assam State area. I look like a local and this was everybody's obsession by the amount of locals asking me where is that mound located and how to get there, equally confused as well with the separate entrances. I suggest visiting this site first if you come early especially on weekends when the site gets more local visitors and escape to the ASI area for peace and quiet. I visited on the month of January when was an unusual tiger sighting in the area so I ventured to the outer reaches of Assam State site, I was followed by guards who didnt want me go as far as mound 88 to 90. At the ASI side, the most interesting is mound 2 which is covered in blue tarpaulin as its still under excavation but there's an information board near that site where you can read and see photos of the artifacts they have excavated from there.
By public transport, take a bus from Sibsagar bus stand heading to the city of Sonari (60 rupees) and asked to be dropped at Charaideo Moidams. The site is about 900 meters walk from the highway. Do the same thing heading back but I highly recommend visiting the beautiful Kareng Ghar, a pyramid-shaped palace built for the Ahom royalty at Gargaon/Simaliguri which is in between Charaideo and Sibsagar.