Currently, different scripts are used to write Northern Thai.
Northern Thai is traditionally written with the Tai Tham script, which in Northern Thai is called tua mueang (ᨲᩫ᩠ᩅᨾᩮᩥ᩠ᩋᨦ ตั๋วเมือง /tǔa.mɯ̄aŋ/) or tua tham (ᨲᩫ᩠ᩅᨵᩢᨾ᩠ᨾ᩺ ตั๋วธัมม์ /tǔa.tʰām/).
However, native speakers are presently illiterate in the traditional script; therefore, they instead use the Thai script to write the language.
In Laos, the Lao script is commonly used to write Northern Thai.

Some problems arise when the Thai script is used to write Northern Thai.
In particular, Standard Thai script cannot transcribe all Northern Thai tones.
The two falling tones in Northern Thai correspond to a single falling tone in Thai.
Specifically, Northern Thai has two types of falling tones: high-falling tone (˥˧) and falling tone (˥˩).
However, Thai lacks the distinction between the two falling tones, not having a high-falling tone (˥˧).
When using Thai script to write Northern Thai tones, the distinction of the two falling tones is lost because Thai script can only indicate a low falling tone (˥˩).
As an example, the tonal distinction between /ka᷇ː/ (ก้า (ᨠᩖ᩶ᩣ กล้า) "to be brave") and /kâː/ (ก้า (ᨣ᩵ᩤ ค่า) "value") is lost when written in Thai since as only /kâː/ (ก้า) is permitted.
Consequently, the meaning of ก้า is ambiguous as it can mean both "to be brave" and "value".
Similarly, /pa᷇ːj/ (ป้าย (ᨸ᩶ᩣ᩠ᨿ ป้าย) "sign") and /pâːj/  (ป้าย (ᨻ᩵ᩣ᩠ᨿ พ่าย) "to lose") have the same problem and only /pâːj/ (ป้าย) is permitted.
As a result, the spelling ป้าย is ambiguous because it can mean both "sign" or "to lose".
Such tonal mergence ambiguity is avoided when the language is written with the Northern Thai script.
Currently, different scripts are used to write Northern Thai. Northern Thai is traditionally written with the Tai Tham script, which in Northern Thai is called tua mueang (ᨲᩫ᩠ᩅᨾᩮᩥ᩠ᩋᨦ ตั๋วเมือง /tǔa.mɯ̄aŋ/) or tua tham (ᨲᩫ᩠ᩅᨵᩢᨾ᩠ᨾ᩺ ตั๋วธัมม์ /tǔa.tʰām/). However, native speakers are presently illiterate in the traditional script; therefore, they instead use the Thai script to write the language. In Laos, the Lao script is commonly used to write Northern Thai.
Some problems arise when the Thai script is used to write Northern Thai. In particular, Standard Thai script cannot transcribe all Northern Thai tones. The two falling tones in Northern Thai correspond to a single falling tone in Thai. Specifically, Northern Thai has two types of falling tones: high-falling tone (˥˧) and falling tone (˥˩). However, Thai lacks the distinction between the two falling tones, not having a high-falling tone (˥˧). When using Thai script to write Northern Thai tones, the distinction of the two falling tones is lost because Thai script can only indicate a low falling tone (˥˩). As an example, the tonal distinction between /ka᷇ː/ (ก้า (ᨠᩖ᩶ᩣ กล้า) "to be brave") and /kâː/ (ก้า (ᨣ᩵ᩤ ค่า) "value") is lost when written in Thai since as only /kâː/ (ก้า) is permitted. Consequently, the meaning of ก้า is ambiguous as it can mean both "to be brave" and "value". Similarly, /pa᷇ːj/ (ป้าย (ᨸ᩶ᩣ᩠ᨿ ป้าย) "sign") and /pâːj/  (ป้าย (ᨻ᩵ᩣ᩠ᨿ พ่าย) "to lose") have the same problem and only /pâːj/ (ป้าย) is permitted. As a result, the spelling ป้าย is ambiguous because it can mean both "sign" or "to lose". Such tonal mergence ambiguity is avoided when the language is written with the Northern Thai script.
Northern Thai language