For this installment of Know Your Dictionary we have the section called simply "ความหมาย" in the original introduction to Royal Institute Dictionary 1999 (พจนานุกรม ฉบับราชบัณฑิตยสถาน พ.ศ. ๒๕๔๒). Now, ความหมาย means "meaning(s)". However, I decided to go with the word "sense" because it's commonly used in a dictionary context to refer to distinct meanings of an entry. Also, sometimes RID99's use of sense or meaning (ความหมาย) vs. definition (บทนิยาม) doesn't perfectly match how I would use them in English. As in other installments, I have tried to translate closely and consistently, but I may have made a few concessions for style. (You can read the original Thai here.)
Part 5: Word senses
1. In defining words with many senses, definitions that are constantly used and are thought to have prominent meanings are normally ordered first. But there are some exceptions where it is intended to show the history of senses, in which case the sense that is thought to be the original sense might be first, followed by the origin, opposites, or collocates (if there are any). Effort has been made to give specific examples for uncommon words.
2. For words with numerous senses that include plant or animal names, definitions of plants and animal names are separated from other definitions, by elevating that word as a separate headword, see for example แก้ว.
3. Abbreviations in parentheses tell the characteristics of a word used in a specific context, e.g. (โบ) (แบบ) (กฎ). If it comes before the part of speech, that means that every definition is used on only in the context specified in parentheses, e.g. เข้า ๒ (โบ) น. ข้าว; ขวบปี. If it comes after the part of speech, only the definitions before the semicolon are used in the context specified in parentheses, e.g. ข้าราชการ น. (โบ) คนที่ทำราชการ ตามทำเนียบ; ผู้ปฏิบัติราชการในส่วนราชการ;...
4. Words that are the plant and animal names follow these definition rules:
A. Plants from different families with the same name are defined under the same headword, but are differentiated by a number in parentheses, e.g. กระโดงแดง น. (๑) ชื่อไม้ต้นขนาดใหญ่... (๒) ชื่อไม้ต้นขนาดกลาง ... B. Animals with the same name that are the same type of animal, but are from different species or families, are defined under the same headword, but separated by a number in parentheses, e.g. กด ๒ น. (๑) ชื่อปลาไม่มีเกล็ด ... (๒) ชื่อปลาน้ำจืดบางชนิด ... C. Animals with the same name but are a different type of animal are not defined under the same headword, but are given different headwords by type along with separate definitions. See for example แก้ว and จะละเม็ด.
5. Inclusion of sub-entries of plant and animal names follows these rules:
A. Sub-entries of plants or animals are of the same family as the headword, e.g. กระโดน has the subhead กระโดนดิน, which is a plant of the same family, or, หมอ ๓ has the subhead หมอตาล, which is an animal of the same family. B. If a plant or animal name is a class term for plants or animals with similar features of many species or many families, sub-entries must have a meaning related to the headword, which may be of a different species or family from the headword, e.g. จันทน์ has the subheads จันทน์กะพ้อ, จันทน์ขาว, จันทน์ชะมด, etc., or, เขียว ๓ has the subhead เขียวหางไหม้.
From point 1 we learn about sense ordering. This is important because dictionaries generally fall into one of two camps: historical order or frequency order. In the first camp, senses are ordered by earliest known text citation (OED, for example); in the second camp, the most commonly used senses are listed first. We learn that RID is a mix of both. I'm not sure how common this type of organization is, but I find it distressing because so far as I know there is no way to know which is which. We can't assume one or the other without some kind of notation. So as I see it, this boils down to mean that, unfortunately, there is not a ton we can learn from sense ordering in RID99. If the first sense is a commonly used sense, it's probably safe to assume that they are ordered by (rough) frequency. Unfortunately again, I don't think there is any empirical evidence behind their ordering, so even the frequency ordering is probably based only on the sense of the committee members as to which words are more common.
The rest is mostly explanation of notation, which is useful. Like how to interpret the scope of a given usage note based on surrounding punctuation (see point 3), or the genetic relationships of certain flora and fauna with their sub-entries.