I like the table calendar which is distributed for free by Bangkok Bank to their customers. The design is clean and allows ample space to jot down important appointments and reminders. In terms of usability (clean design and material that is easy to write on, with sufficient spacing), the calendar is better than even the commercialised calendars sold out there.
As it is now the month of July, let me show you the spread of the Thai calendar from July 2019 to December 2019, also known as the Thai year 2662.

The motif being used is painting of various scenery.

It is done in a form of abstract style.

July 2019 / กรกฎาคม 2662:
Buddhist observation dates in July: 1st, 9th, 16th, 24th and 31st.

August 2019 / สิงหาคม 2662:
Buddhist observation dates in August: 8th, 15th, 23rd & 29th.

September 2019 / กันยายน 2662:
Buddhist observation dates in September: 6th, 13th, 21st & 28th.

October 2019 / ตุลาคม 2662:
Buddhist observation dates in October 2019: 6th, 13th, 21st & 27th.

November 2019 / พฤศจิกายน 2662:
Buddhist observation dates in November 2019: 4th, 11th, 19th & 26th.

December 2019 / ธันวาคม 2662:
Buddhist observation dates in December 2019: 4th, 11th, 19th & 25th.

Being a Buddhist country, the Buddhist observation dates are marked in all standard Thai calendars (the yellow and grey full/ half circle which corresponds to the cycle of the moon). On average, there are about 4 (or sometimes 5) observation dates in a month where some would make time to visit temples to practice meditation, join in for chanting or help out.
Hopefully you would find the calendar visuals useful especially if you are staying in another country where such calendars are not easily available. These calendars are written using standard numbers. If you wish to view the calendar where the numbers are written in Thai, so far in Thailand there is only one featuring the late Venerable Buddhadasa which are sold in Thai bookstores such as SE-ED, NAIIN and B2S during end/ beginning of each year.